The Tropical Rainfall Measuring Mission's (TRMM) Microwave Imager (TMI) was a passive microwave sensor designed to provide quantitative rainfall information over a wide swath under the TRMM satellite. The TMI measured the intensity of radiation at five separate frequencies: 10.7, 19.4, 21.3, 37, 85.5 GHz and had a 547 mile (878-kilometer) wide swath on the surface. By carefully measuring the minute amounts of microwave energy emitted by Earth and its atmosphere, TMI quantified atmospheric water vapor, cloud water, and rainfall intensity.
